In a conventional manner of analyzing dialed digits plural groups of relays are provided, each group being associated with a specified digit position, such as the unit position, tens position, hundreds position, etc. and binary divider chains, coupled to the relay groups, are employed for analyzing the dialed digits. Moreover, separate counters, associated with the relay-divider groups are employed for counting the received digits. Unfortunately, with this type of arrangement, a considerable amount of counting and storage circuitry is necessary for carrying out the analysis of the dialed digits for processing by the system.
In our copending application entitled Electronic Private Automatic Branch Exchange application Ser. No. 431,928, filed Jan. 9, 1974, now U.S. Pat. No. 3,943,297, there is described a new and improved electronic private automatic branch exchange telephone system wherein calls are handled on a time shared basis. In this system, in place of the usual switching matrix, which is associated with the common control for both switching and talking functions, the switching matrix transmits only the talking signals between the parties. The common control components are associated with each call continuously throughout the call and the status of each calling and called party is continuously monitored and processed on a time shared basis. In this system, an ING and ED memory is employed to store information relative to the called and calling numbers. Status circuitry, which forms a part of the general common control, provides appropriate signals representative of the status of each call during a prescribed time slot associated with the junctor which has been selected to handle the call connection. Depending upon both the present status of the call and information signals relative to any changes in the call as the call progresses, such as a change from on-hook condition to off-hook and dial tone, dialing, busy testing, ringing, etc., the common control supplies signals to and receives signals from the various components used for establishing and maintaining a call connection during each time slot associated with the junctors which are used for the call connection.
When a calling party desires a connection with another called number, the ING and ED memory is employed to store the numerical identification of the calling and called parties so that appropriate action may be taken by the common control during the establishment of the call. The common control acts upon the contents of the ING and ED memory at the appropriate junctor time slot assigned for that particular call. Of course, one of the basic operations which must be carried out in the establishment of a call is the identification of the called number and the processing of the dialed information.
The present invention relates particularly to an arrangement for analyzing and decoding dialed information so that the call may be properly established under the control of the common control and the associated circuit components coupled therewith. The present invention is particularly useful in a time shared PBX system and may be employed in the system described in our above referred to application entitled Electronic Private Automatic Branch Exchange.